The present invention relates to a cross-section controlled multi-jet injection valve comprising a valve body and a valve needle that is axially movable within the valve body, whereby the valve needle opens the valve in a direction towards the combustion chamber. The sealing seat of the valve needle corresponds to the injection cross-section of the fuel.
It has been known from DE-OS No. 29 49 596 to open the valve by moving the valve needle in the direction of the combustion chamber. The sealing seat is conically shaped and represents at the same time the outlet opening that corresponds to the fuel injection cross-section. With such an injection valve it is not possible to maintain the fuel pressure at a constant level over the entire performance range. The formation of the fuel/air mixture, and thus the fuel preparation, is impaired because the injected fuel jet in the shape of a hollow cone is not divided resulting in an unfavorable ratio of the large circumference of the annular groove to the injection cross-section.
From DE-OS No. 27 10 138 it has also been known to provide a hollow needle having a valve needle coaxially guided inside the hollow needle. The hollow needle may be supplied with fuel pressure from a pressure chamber via a pressure shoulder. Upon a predetermined fuel pressure the hollow needle opens against the force of a first pressure spring thus opening the path for the fuel to the valve needle and to a first injection bore. At a higher load of the combustion engine and a resulting higher fuel pressure generated by an injection pump the valve needle opens against the force of a second pressure spring. The injection of fuel into the combustion chamber then occurs via a second injection bore until, due to the decreasing fuel pressure, the valve needle closes and the injection is terminated. With such an injection valve a stepping of the injected amount of fuel with respect to the direction and shape of the fuel jet is achieved. However, it is disadvantageous that the fuel pressure before the injection bores may not be maintained at a constant high value over the entire performance range. A further disadvantage is the use of multiple injection ports. When under partial load only one bore is used for the fuel injection the second unused bore which only operates during full load tends to form soot.
It is therefore an object of the present invention to provide an injection valve of the aforementioned kind with which the injected amount of fuel is divided into multiple jets whereby a favorable ratio of fuel injection cross-section to the circumference of the respective cross section is provided and at the same time a constant injection pressure before the injection channels is maintained over the entire performance range.